How to Protect Trees During Winter

Thu, December 03, 2015 2:06 PM | Danielle Corral

As night temperatures in Phoenix fall into the thirties, it is important to protect young trees from such cold weather. Temperatures below 32 degrees for a prolonged time or over several nights can freeze tree buds/blossoms, fruit, leaves, and twigs. While the trees in our Shade Tree Program are desert-adapted and can, therefore, typically withstand freezing temperatures, young saplings can be vulnerable to the cold weather especially if they haven’t gone into winter dormancy and are, therefore, still actively growing. Below are things you can do to protect your trees from frost:

  • Cover your trees with a sheet, light blanket, or burlap sack. Hardware stores  sell sheets made of light, porous material specifically for frost protection but feel free to use whatever you have on hand except for anything made of plastic. Plastic traps moisture in and can damage the tree (the captured moisture can turn to frost). Also, thick blankets or covers can soak up moisture, become heavy, and press down on the tree. Ideally, you want the cover to touch the ground to retain the warmth under the cloth and around the tree (refer to the picture on the right and the diagram below). Remove the cover later in the morning when there is full sunlight and preferably when temperatures are warmer. Some of the coldest temperature occur at daybreak so if you can, wait a bit. Do not leave trees covered all day as this can damage them.

  • If your tree gets frost bitten, do NOT trim the damaged parts as they still provide protection for the remaining living parts of the tree. Wait until the spring or when you regularly prune your tree. Make sure to water your trees regularly during winter. Dehydrated trees are more susceptible to frost-- frost damage occurs when ice crystals form on the leaf surface drawing moisture from the leaf tissue so if a tree is already dehydrated, the additional dehydration damages or kills it. Wet soil also absorbs heat during the day so water your plants in the morning and do not overwater. Refer to our blog on How to Properly Water Your Trees.
  • For large trees or frost-sensitive ones such as citrus trees, string 100-watt electric outdoor light bulbs, such as Christmas lights (pictured right). Not only are you decorating for the holidays but you are warming your trees.  Make sure the lights are not too close to the trunk or branch that it could burn it.
  • Place mulch around deciduous trees (like our shade trees) to prevent them from breaking winter dormancy by insulating against fluctuating surface soil temperatures. However, do not place mulch around citrus trees, as it will hinder the capturing of heat that will protect the plant.

If your tree is damaged or you have other questions, feel free to post them on our ask the arborist forum here.

 

References:

http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1002.pdf

http://www.vpaaz.wildapricot.org/STBlog/3111687

http://canopy.org/caring-for-trees/protecting-trees-from-freeze/

http://phoenix.about.com/od/desertplantsandflowers/qt/frostplants.htm

http://www.motherearthnews.com/organic-gardening/how-to-protect-fruit-trees-from-frost-zb0z1302zsor.aspx

http://vpaaz.org/STForum (ask the arborist forum) 

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